An inflatable vehicle occupant protection device, such as an air bag, is part of an apparatus which further includes a crash sensor and an inflator. The crash sensor senses vehicle conditions that indicate the occurrence of a crash. When the crash sensor senses a crash-indicating condition of at least a predetermined threshold level, the inflator is actuated. The inflator then emits inflation fluid which inflates the air bag into the vehicle occupant compartment to help protect an occupant of the vehicle.
An air bag and an inflator are typically assembled together as parts of an air bag module which is separate from the crash sensor. The module is installed in a vehicle part adjacent to the vehicle occupant compartment. The module may thus be installed in a vehicle instrument panel, a vehicle steering column, or, as in the present invention, in a vehicle seat.